Document WO 2008/141411 discloses a lubricating system for lubricating the chain saw of a felling head at the end of a boom assembly of a forest machine. This system comprises a grease reservoir, a grease feeder and a grease pump, which are all placed in connection with the engine compartment of the base machine. The feeder is connected to the grease pump in such a way that it supplies grease from the grease reservoir via the inlet of the grease pump to the grease pump. The grease pump is connected to the chain saw to be lubricated, by a hose between the outlet of the grease pump and the chain saw at the end of the boom assembly of the forest machine.
The length of the hose system in the forest machine, from the engine space of the base machine to the work implement placed at the end of the boom assembly, may be even 10 to 15 meters. As a result, there is a delay in the supply of the lubricant by a pump placed in the base machine, between the time of turning on the pump and the time of supply of grease to the chain saw to be lubricated at the end of the boom assembly. Therefore, at times, the chain of the chain saw to be lubricated may need to operate under insufficient lubrication conditions. This will increase the wear of the chain and the guide bar, and at worst, it may cause overheating and damage of the chain saw, because in modern forest machines, the speed of motion of the chain of the chain saw is very high, and when cutting a tree, the chain of the chain saw is pressed towards the edge of the guide bar of the chain saw, wherein those parts of the chain saw which move in relation to each other heat up strongly, unless sufficient lubrication is provided between them. On the other hand, a long hose system dispenses lubricant in excess to the lubrication target although the sawing function is at times not in use, which causes waste of the lubricant.
At present, such lubrication systems are also known, in which the pump and the lubricant reservoir are placed in the work implement (e.g. harvester head) at the end of the boom assembly. In such a solution, as presented in e.g. US 2010/0282367, the supply of lubricant can be made to function better in real time, because the lubricant pump is positioned close to the target to be lubricated. In view of the efficient use of the forest machine, however, it is advantageous that the work implement placed at the end of the boom assembly is as light weight as possible. A lubricating system placed in the work implement will increase the weight of the work implement, particularly if the lubricant reservoir included in the lubrication system is relatively large. On the other hand, if the size of the lubricant reservoir is reduced, the reservoir has to be filled more frequently, which, in turn, is not advantageous in view of the efficiency of the work to be performed with the forest machine.